![Page 1: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/1.jpg)
Spin superconductor and electric dipole superconductor
Xin-Cheng Xie ( 谢心澄 )
International Center for Quantum Materials,School of Physics, Peking University
![Page 2: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/2.jpg)
Part I: Spin current and spin
superconductor
In collaboration with:Qing-feng Sun (Peking University)Zhao-tan Jiang (Beijing Institute of Technology) Yue Yu (Fudan University)
![Page 3: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/3.jpg)
Outline
• Basic Properties of Spin Current
• Spin-Superconductor (SSC) in a
Ferromagnetic Graphene
• Results and Discussion
• Conclusion
![Page 4: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/4.jpg)
)( IIeIe
Spin Current
Spin-up electrons move in one way and same number of spin-down electrons move in the opposite way, thus charge current vanishes, but spin current is doubled.
![Page 5: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/5.jpg)
Y.K.Kato et al., Science, 306, 1910 (2004)
Carriers with opposite spins are separated by spin-orbit coupling
ij spin ijk kJ E
Murakmi et al, Science 31, 1248 (2003)
The spin Hall effect
![Page 6: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/6.jpg)
1. charge continuity equation:
definition of charge current density:
2. Is there a spin continuity equation? How to define the spin current density?
Similar as for the charge continuity equation,we calculate : , where is the localspin density. Then:
Spin current density and the spin continuity equation
![Page 7: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/7.jpg)
Take:
We have:
We have:
This is the spin continuity equation
*
![Page 8: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/8.jpg)
Notice, due to
**
![Page 9: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/9.jpg)
Both linear and angular spin currents can induce electric fields:
*
*
![Page 10: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/10.jpg)
A conserved physical quantity :
Let us apply acting on the equation :
then :
Introduce :
We have :
The current of the spin divergence is a conserved quantity ! ! !
![Page 11: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/11.jpg)
+ + + + + + + + -------------
The total electric field can be represented as :
The meaning of is: an equivalent magnetic charge.
Through the measurement of , can be uniquely obtained ! ! !
![Page 12: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/12.jpg)
Spin superconductor in ferromagnetic graphene
S-wave Cooper Pairs, 2e, spin singlet, BCS ground state
Exciton, electron-hole pair, charge-neutral, spin singlet or triplet
A spin triplet exciton condensate is named as
Spin-Superconductor (SSC)
General drawback of the exciton condensate
in many physical systems is its instability because of
the electron-hole (e-h) recombination
Typical exciton lifetime: picosecond~microsecond, short
![Page 13: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/13.jpg)
Exciton in normal graphene
Spin-singlet exciton excitation:The charge carriers are spin-unpolarized in normal graphene
![Page 14: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/14.jpg)
In the ferromagnetic (FM) graphene,the carriers are spin polarized.
Electron-like
Hole-like
Exciton:
These positive and negative carriers attract and form excitons that are stable against the e-h recombination due to the Coulomb interaction.
If a carrier jumps from the electron-like state to the hole-like one, the total energy of the system rises, which prevents the e-h recombination and means the exciton in the FM graphene is stable.
![Page 15: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/15.jpg)
Spin-Superconductor (SSC)
• Hamiltonian
with
![Page 16: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/16.jpg)
The total mean field Hamiltonian
The corresponding energy spectrum is shown by the solid curves.
An energy gap is opened.
This means the exciton condensed state of the e-h pairs is more stable than the unpaired state.
![Page 17: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/17.jpg)
The spin current is dissipationless and the spin resistance is zero.
The ground state of the FM graphene is a neutral superconductor with spin ћ per pair ------SSC
The energy gap can be obtained self-consistently
![Page 18: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/18.jpg)
Self-consistent numerical results
![Page 19: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/19.jpg)
Result and Discussion-- 1. Meissner Effect
The criterion that a superconductor differs from a perfect metal
Described by the London equations.
Is there a Meissner-like effect for the SSC?
BbJ
Eat
J
c
c
d
d
![Page 20: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/20.jpg)
Consider a SSC with the superfluid carrier density in an external electric field E and a magnetic field B
Magnetic force on a spin carrier
(a)
(b)
![Page 21: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/21.jpg)
Example for this electric Meissner effect:
Consider a positive charge Q at the origin andan infinite FM graphene in the x-y plane at z = Z
super-spin-current
![Page 22: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/22.jpg)
SSF/Normal Conductor/SSF junction
Result and Discussion-- 2. Josephson Effect
![Page 23: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/23.jpg)
There is a super-spin-current flowing through the junction that resembles the Josephson tunneling in a conventional superconductor junction.
Fig. 3(c) shows the super-spin-current Js can also be observed in non-zero md as far as Δ ̸= 0 and Δϕ ̸= 0, π.
![Page 24: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/24.jpg)
Step 1: the form of the free energy3
s sF d r f
Note: The fourth term is the kinetic energy.
electron charge in external electric and magneitic filed:
magnetic moment in external electric and magneitic filed:
canonical
equation
Ginzburg-Landau equations of the spin superconductor
![Page 25: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/25.jpg)
Step 2: Derivate the Ginzburg-Landau equations by variational method (a) Variate the free energy by , we get the first Ginzburg-Landau equation:
with the boundary condition:
(b) Variate the free energy by , we we get the second Ginzburg-Landau equation:
If we definite
we getthe second GL equation describes the equivalent charge induced by the super-spin-current.
![Page 26: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/26.jpg)
Substitute
we have
, the generalized London equation
if
the second London equation
if is independent of
![Page 27: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/27.jpg)
Measurement of Spin Superconductor State
Four-terminal device used to measure the SSC state (1,2,3,4 denote four terminals)
Based on the device in the paper of Nature 488, 571 (2007)
zero spin resistance spin supercurrent
1 2 3 4
Scheme
Non-local resistance measurement
Apply a current IeIe between two right electrodes 3 and 4; Measure the bias VV between two left electrodes 1 and 2.
Why is the bias VV generated?
![Page 28: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/28.jpg)
Resistance versus the temperature
Top view of the four-terminal device
T>Tc, normal state, R23 is small
T<Tc, SSF state, R23 is large due to the gap
R23 ~
![Page 29: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/29.jpg)
Non-local resistance
T>Tc, non-local resistance is small because the normal state has the spin resistance
T<Tc, non-local resistance sharply increases
When graphene is in the SSC the non-local resistance is very large, because that the spin current can dissipationlessly flow through the super-spin-fluid region.
Here we emphasize that the changes of the normal resistance and non-local resistance are sharp, similar as the resistance change when a sample enters from a metal phase into a superconducting phase. Thus, these resistances can easily be measured in experiments.
In addition, for T < Tc the non-local resistance is independent of the length of the red strip, implying the zero spin resistance in the spin-superfluid state.
![Page 30: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/30.jpg)
Display Landau level structure instead of linear dispersion.
*
B=0 B≠0
What is the effect of the formation of the LLs on the spin superconductor?
Graphene under a magnetic field
![Page 31: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/31.jpg)
Each LL is fourfold degenerate due to the spin and valley. The zeroth LL locates at the charge neutrality point and has the equal electron and hole compositions. The e-e interaction and Zeeman effect can lift the LL degeneracy.
Due to the spin split, now a +↑ LL is occupied by electrons and a −↓ LL is occupied by holes, there is a pair of counter-propagating edge states.
These edge states can carry both spin and charge currents. So the sample edge is metal.
![Page 32: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/32.jpg)
J.G. Gheckelsky, et.al. Phys. Rev. Lett. 100, 206801 (2008).
The Hall conductance has a plateau with the value zero, but the longitudinal resistance shows an insulating behavior, it increases quickly with decreasing temperature.
However, experiments have clearly shown an insulating behavior.
![Page 33: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/33.jpg)
Many experiments show the same results.
A.J.M. Giesbers, et.al. Phys. Rev. B. 80, 201203(R) (2009).
also see: Phys. Rev. Lett. 107, 016803(2011); Science 330, 812(2010); Science 332, 328 (2011); etc.
![Page 34: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/34.jpg)
Hall conductivity in Graphene , Zero-Energy Landau Level
PRL , 100 , 206801 (2008)N. P. Ong
![Page 35: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/35.jpg)
PRL , 104 , 066801 (2010)P. Kim
Hall conductivity in Bilayer Graphene ,Zero-Energy Landau Level
![Page 36: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/36.jpg)
Electrons and holes are both spin up. With an e-h attractive interaction, e and h may form an e-h pair and then condense into a spin superconductor at low T.
*
*In present case, the carriers are both electrons and holes.
![Page 37: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/37.jpg)
A gap opens in the edge bands. Now both edge and bulk bands have gaps, it is a charge insulator, consistent with the experimental results.
![Page 38: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/38.jpg)
Resistance and nonlocal resistance:
Insulator at Dirac points at low T; the nonlocal resistance rapidly increases at low T, showing that the spin current can flow through the graphene.
These experimental results can be explained by a spin superconductor.
D.A. Abanin, et.al., Science 332, 328 (2011)
![Page 39: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/39.jpg)
Summary
We predict a spin superconductor (SSC) state in the ferromagnetic graphene, as the counterpart to the (charge) superconductor. The SSC can carry the dissipationless super-spin-current at equilibrium.
BCS-type theory and Ginzburg-Landau theory for the SSC are presented, and an electrical ‘Meissner effect’ and a spin-current Josephson effect in SSC device are demonstrated.
![Page 40: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/40.jpg)
Part II:Theory for
Electric Dipole Superconductor (EDS) with an application for bilayer excitons
In collaboration with:Qing-feng Sun (Peking University)Qing-dong Jiang (Peking University) Zhi-qiang Bao (IOP, CAS)
![Page 41: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/41.jpg)
Outline
Pairing condensation
Exciton condensation in double-layer systems
![Page 42: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/42.jpg)
Pairing CondensationPairing Condensation
Attractive interaction between fermions - Cooper problem (two-body problem) : bound states
- Normal fluid is unstable at low T
Examples - Superconductor (e-e pair) : e-ph interaction
- Exciton (electron-hole pair) : Coulomb interaction
![Page 43: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/43.jpg)
Exciton Condensation in Double-layer SystemExciton Condensation in Double-layer System
Tunneling Vanished Hall voltage
Spielman et al, PRL (2000)
Tutuc et al, PRL (2004)
Kellogg et al, PRL (2004)
GaAs/AlGaAs d=9.9nmd=7.5nmGaAs/AlAs
![Page 44: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/44.jpg)
Exciton Condensation in Double-layer SystemExciton Condensation in Double-layer System
Coulomb drag experiment
D.Nandi et al, Nature (2012)
GaAs/AlGaAs d=10nm
is the drive current is the drag current
At small
Perfect drag!
![Page 45: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/45.jpg)
Exciton Condensation in Double-layer SystemExciton Condensation in Double-layer SystemHowever, None of these measurement can directly confirm the existence of exciton superfluid.
We need to discover the basic characteristics of exciton superfluid.
G-L equation
Meissner-type effect
Zero dipole resistance
Dipole Josephson effect
London equation
We view the excitons in bilayer systems as electric dipoles. Taking this point of veiw, we get
![Page 46: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/46.jpg)
London-type equation for dipole superconductorLondon-type equation for dipole superconductor
The force on an electric dipole
Define a super dipole current density
Time derivative of
The curl of
![Page 47: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/47.jpg)
Ginzburg-Landau equationGinzburg-Landau equation
Hamiltonian
Free energy density
Minimize the free energy with respect to and
Lagrangian
![Page 48: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/48.jpg)
Ginzburg-Landau equationGinzburg-Landau equation
First G-L type equation
Second G-L type equation
Super electric dipole current
Assume
The London equation can be obtained
(1)
(2)
![Page 49: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/49.jpg)
Meissner-type Effect:Meissner-type Effect:Screen magnetic field gradientScreen magnetic field gradient
![Page 50: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/50.jpg)
Comparison between SC and EDSComparison between SC and EDS
SC screen magnetic field B EDS screen magnetic field gradient
![Page 51: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/51.jpg)
Zero Dipole Resistance Zero Dipole Resistance Schematic figure In the electric dipole superconductor region
but
Closing the current suddenly willinduce a super electric dipole current
![Page 52: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/52.jpg)
Electric dipole Current Josephson EffectElectric dipole Current Josephson Effect
The frequency
The same as superconductor!
Analogy
![Page 53: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/53.jpg)
SummarySummary
1. We developed a general theory for electric dipole superconductor including London-type equation and Ginzburg-Landau equations.
2. View the bilayer excitons as electric dipoles, and we get three novel effects . 3. These effects are the characteristics of EDS, and can be used to justify the existence of exciton superfluid.
![Page 54: Spin superconductor and electric dipole superconductor Xin-Cheng Xie ( 谢心澄 ) International Center for Quantum Materials, School of Physics, Peking University](https://reader038.vdocuments.site/reader038/viewer/2022102622/56649d355503460f94a0c860/html5/thumbnails/54.jpg)
Thank you!